CN105576623B - Self-adaptive half-wavelength line differential protection method based on time difference method - Google Patents

Self-adaptive half-wavelength line differential protection method based on time difference method Download PDF

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CN105576623B
CN105576623B CN201610066743.8A CN201610066743A CN105576623B CN 105576623 B CN105576623 B CN 105576623B CN 201610066743 A CN201610066743 A CN 201610066743A CN 105576623 B CN105576623 B CN 105576623B
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line
current
time difference
fault point
fault
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CN105576623A (en
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梁旭明
郭雅蓉
柳焕章
李肖
周泽昕
杜丁香
王德林
李晶
李会新
李仲青
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STATE GRID CENTER CHINA GRID Co Ltd
State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
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STATE GRID CENTER CHINA GRID Co Ltd
State Grid Corp of China SGCC
China Electric Power Research Institute Co Ltd CEPRI
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Priority to PCT/CN2016/089672 priority patent/WO2017128631A1/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/26—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured
    • H02H7/261—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations
    • H02H7/263—Sectionalised protection of cable or line systems, e.g. for disconnecting a section on which a short-circuit, earth fault, or arc discharge has occured involving signal transmission between at least two stations involving transmissions of measured values
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/02—Details
    • H02H3/04—Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned
    • H02H3/042—Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned combined with means for locating the fault
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
    • G01R31/085—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution lines, e.g. overhead
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/08—Locating faults in cables, transmission lines, or networks
    • G01R31/088—Aspects of digital computing
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
    • H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
    • H02H3/28—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus
    • H02H3/30—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus using pilot wires or other signalling channel
    • H02H3/305—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at two spaced portions of a single system, e.g. at opposite ends of one line, at input and output of apparatus using pilot wires or other signalling channel involving current comparison
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/22—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices
    • H02H7/226—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for distribution gear, e.g. bus-bar systems; for switching devices for wires or cables, e.g. heating wires

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Power Engineering (AREA)
  • Mathematical Physics (AREA)
  • Theoretical Computer Science (AREA)
  • Emergency Protection Circuit Devices (AREA)
  • Optical Communication System (AREA)

Abstract

The invention relates to a self-adaptive half-wavelength line differential protection method based on a time difference method; because the half-wavelength power transmission has long electrical distance, the action time of the protection starting elements on two sides of the line has obvious time difference after the fault occurs, and the position of the fault point can be estimated through the action time difference of the protection starting elements on two sides according to the wave propagation principle. According to the long-line equation, the voltage and the current at the protection installation positions on the two sides of the line can be compensated to a fault point, the current value at the fault point is obtained, and then the differential current is calculated. Because the sensitivity of the differential protection criterion of the fault at different points of the line is different, the braking coefficient and the threshold value of the differential protection are adaptively changed according to the different positions of the fault points, and the sensitivity of the differential protection to the whole line of the line is ensured.

Description

Self-adaptive half-wavelength line differential protection method based on time difference method
The technical field is as follows:
the invention relates to the field of relay protection, in particular to a self-adaptive half-wavelength line differential protection method based on a time difference method.
Background art:
Half-Wavelength AC Transmission (HWACT) refers to three-phase AC Transmission in which the electrical distance of Transmission is close to one power frequency Half-wave, i.e., 3000km (50 cycles) or 2600 km (60 cycles) over a long distance. Compared with the medium-length (hundreds of kilometers) AC transmission, the ultra-long-distance AC transmission has several distinct characteristics and remarkable advantages, such as no need of installing reactive compensation equipment; an intermediate switching station is not required; the overvoltage level is not high; excellent economy, etc. To realize the engineering application of half-wave power transmission, further research on the relay protection technology of the line is needed.
The current differential protection is widely applied as the main protection of the medium-length alternating-current transmission line, but the voltage difference of all positions along the half-wavelength transmission line cannot be ignored, the traditional capacitance current compensation method is not applicable any more, and aiming at the problem, the invention provides a self-adaptive half-wavelength line differential protection method based on a time difference method.
The invention content is as follows:
the invention aims to provide a self-adaptive half-wavelength line differential protection method based on a time difference method, which can self-adaptively change the braking coefficient and the threshold value of differential protection according to different fault point positions and ensure that the differential protection has sensitivity to the whole line of the line.
In order to achieve the purpose, the invention adopts the following technical scheme: a self-adaptive half-wavelength line differential protection method based on a time difference method comprises the following steps:
1) estimating a fault point of the half-wavelength power transmission line;
2) determining a current at a fault point;
3) according to the fault point LFMAdaptive adaptationA variable braking coefficient and a threshold value.
Estimating the fault point by using a time difference method in the step 1); determining the action time T of the protection starting elements at two sides of the line according to the action time of the protection starting elements by the time difference methodMAnd TNThereby estimating the fault location.
The criterion of the time difference method for protecting the starting element is shown as the following formula (1):
Figure BDA0000918742410000021
in the formula,. DELTA.iA(t)、ΔiB(t) and Δ iC(t) break variables for A, B, C three-phase currents, respectively; Δ f (t) is a function of the sum of squares of the current break; f. ofsetThe current setting value is obtained.
Calculating the action time T according to the following formulaMAnd TN：
LFM＝((TM-TN)vLight (es)+L)/2 (2)
In the formula, LFMThe distance between the fault point and the M side of the line, L is the length of the half-wavelength line 3000km, vLight (es)Is the propagation speed of light.
In the step 2), the current at the fault point is determined according to the long line equation to obtain the fault point LFMFor the compensation point, compensation is performed using the long line equation.
Determining the current of the fault point according to the following formula:
Figure BDA0000918742410000022
wherein x is LFM；Ix+And Ix-Is the current at the compensation; u shapeM、UN、IMAnd INPhasor values of voltage and current of the M side and the N side of the line respectively; zcIs the wave impedance of the line; γ is the propagation constant of the line.
Current I of the compensation pointx+And Ix-Current differentiation is performed according to the following equation:
Figure BDA0000918742410000031
wherein k is the braking coefficient, IsetIs the differential current threshold.
Adaptively changing a braking coefficient k and a differential current threshold value I according to the following formulaset：
Figure BDA0000918742410000032
Compared with the closest prior art, the technical scheme provided by the invention has the following excellent effects:
by utilizing the self-adaptive half-wavelength line differential protection method based on the time difference method, the problem that the action time of protection starting elements on two sides of a line has obvious time difference after a fault occurs due to the long electrical distance of half-wavelength power transmission is solved; according to the wave propagation principle, the position of a fault point can be estimated through the action time difference of protection starting elements on two sides, so that the current value of the fault point is obtained, and then the differential current is calculated. Because the sensitivity of the differential protection criterion is different when the fault occurs at different points of the line, the braking coefficient and the threshold value of the differential protection are adaptively changed according to the difference of the positions of the fault points, so that the sensitivity of the differential protection to the whole line of the line is ensured, the fault occurrence of the half-wavelength line is reduced, and the loss and inconvenience brought by the fault are reduced.
Drawings
FIG. 1 is a flow chart of a method of an embodiment of the present invention;
fig. 2 is a schematic diagram of adaptively changing a braking coefficient and a threshold value of a differential protection according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples.
Example 1:
the invention of this example proposes a self-adaptive half-wavelength line differential protection method based on a time difference method, the steps of which are shown in fig. 1:
(1) the time difference method protects the action time of the starting element as the time when the protection element senses the fault, and obtains the action time T of the protection starting element at two sides of the lineM、TN. The time difference method protection starting criterion is as follows:
(2) estimating fault location L using time difference methodFM：
LFM＝((TM-TN)vLight (es)+L)2 (2)
(3) By fault point LFMCompensating by using a long line equation to obtain the current I at the compensation pointx+、Ix-：
(4) By means of Ix+And Ix-Carrying out current differential:
Figure BDA0000918742410000043
(5) the braking coefficient and threshold value in the current differential criterion are adaptively determined, as shown in fig. 2:
Figure BDA0000918742410000044
Figure BDA0000918742410000045
finally, it should be noted that: the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting the same, and those skilled in the art should understand that although the above embodiments are referred to: modifications and equivalents may be made to the embodiments of the invention without departing from the spirit and scope of the invention, which is set forth in the claims below.

Claims (3)

1. A self-adaptive half-wavelength line differential protection method based on a time difference method is characterized by comprising the following steps: the method comprises the following steps:
1) estimating a fault point of the half-wavelength power transmission line;
2) determining the current of a fault point;
3) the braking coefficient and the threshold value are adaptively changed according to different fault point positions;
estimating the fault point by using a time difference method in the step 1); determining the action time T of the protection starting elements at two sides of the line according to the action time of the protection starting elements by the time difference methodMAnd TNThereby estimating the fault location;
the criterion of the time difference method for protecting the starting element is shown as the following formula (1):
Figure FDA0002190017560000011
in the formula,. DELTA.iA(t)、ΔiB(t) and Δ iC(t) break variables for A, B, C three-phase currents, respectively; Δ f (t) is a function of the sum of squares of the current break; f. ofsetSetting a current value;
estimating fault location L using time difference methodFM：
LFM＝((TM-TN)vLight (es)+L)/2 (2)
In the formula, LFMThe distance between the fault point and the M side of the line, L is the length of the half-wavelength line 3000km, vLight (es)Is the propagation velocity of the light;
in the step 2), the current at the fault point is determined according to the long line equation to obtain the fault point LFMFor the compensation point, compensation is carried out by using a long line equation;
determining the current of the fault point according to the following formula:
Figure FDA0002190017560000012
wherein x is LFM；Ix+And Ix-Is the current at the compensation; u shapeM、UN、IMAnd INPhasor values of voltage and current of the M side and the N side of the line respectively; zcIs the wave impedance of the line; γ is the propagation constant of the line.
2. The self-adaptive half-wavelength line differential protection method based on the time difference method as claimed in claim 1, characterized in that: current I of the compensation pointx+And Ix-Current differentiation is performed according to the following equation:
Figure FDA0002190017560000021
wherein k is the braking coefficient, IsetIs the differential current threshold.
3. The self-adaptive half-wavelength line differential protection method based on the time difference method as claimed in claim 2, characterized in that: adaptively changing a braking coefficient k and a differential current threshold value I according to the following formulaset：
Figure FDA0002190017560000022
Figure FDA0002190017560000023
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CN106356822B (en) * 2016-10-10 2019-02-05 许继集团有限公司 A kind of deficient range combinations formula guard method of half-wave power transmission route and device
CN107359599B (en) * 2017-07-20 2019-04-09 许继集团有限公司 A kind of difference current time difference modification method, device and differential protecting method, device
CN107394766B (en) * 2017-07-31 2018-07-17 天津大学 A kind of overvoltage method for limiting suitable for half-wave power transmission circuit
CN107482597B (en) * 2017-08-16 2019-12-10 南京国电南自电网自动化有限公司 Half-wavelength transmission line time difference pilot direction protection method
CN110336257B (en) * 2019-07-04 2023-01-31 中国电力科学研究院有限公司 Lightning-proof and abnormal large-number direct-current transmission line protection method and system
CN110501557B (en) * 2019-09-18 2021-07-30 南京国电南自电网自动化有限公司 Anti-electromagnetic interference protection quick start method and system
CN111208387B (en) * 2020-02-17 2022-03-11 国电南瑞南京控制系统有限公司 Distribution network single-phase grounding line selection method based on synchronous phase current fault component comparison
CN111884183A (en) * 2020-07-20 2020-11-03 天津大学 Self-adaptive positive sequence current quick-break protection method for main line of petal-shaped power distribution network
CN112345879B (en) * 2020-09-16 2023-03-14 中国电力科学研究院有限公司 Direct-current transmission line fault direction judgment method and system with strong anti-jamming capability
CN113725816B (en) * 2021-09-08 2022-05-17 西南交通大学 Transformer differential protection method and system based on current phasor difference 2 norm
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